Magnetostriction element and magnetostriction-type vibration powered generator using same

ABSTRACT

A magnetostriction-type vibration powered generator including a power generating section and a frame joined to the power generating section. The power generating section includes a diaphragm formed of non-magnetic material and disposed at a first end of the power generating section, a magnetostriction element disposed at a second end of the power generating section; and a coil wrapped around the magnetostriction element along the longitudinal direction. The frame includes a frame body formed of a magnetic material and joined to a second end of the power generating section. A magnet is provided on the frame body so as to face the magnetostriction element of the power generating section.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of U.S. applicationSer. No. 16/460,145 filed on Jul. 2, 2019 and claims the benefit offoreign priority of Japanese patent application 2018-160992 filed onAug. 30, 2018, the contents of which are incorporated herein byreference.

TECHNICAL FIELD

The technical field relates to a magnetostriction element formed of amagnetostrictive material, and to a magnetostriction-type vibrationpowered generator using same.

BACKGROUND

Recent years have seen the arrival of the Internet of things (IoT), aworld where “things” equipped with autonomous communication functionsautomatically control one another by exchanging information. The spreadof IoT means a society with increasing numbers of IoT devices featuringcommunication functions. IoT devices, such as sensors, require a powersupply to operate. However, the needs for wirings and service time, andthe cost make it difficult to provide power supplies for theseproliferating numbers of devices. This has created a need for a powersupply technology suited for IoT devices in the coming era of IoT.Against this background, an important consideration is a technologycalled “energy harvesting”, a process by which small amounts of energyfrom the everyday environment are converted into electrical power.Vibration is a form of energy source that is constantly produced bymoving objects such as automobiles, trains, machinery, and humans inmany places, and represents an energy source that is not influenced byweather or climate. It is therefore envisioned that a system thatenables vibration-based power to be used as a power supply toapplications coupled to movement of moving objects such as above canopen the door to more effective IoT.

Vibration-based power generation can be divided into four categories:magnetostrictive, piezoelectric, electrostatic induction, andelectromagnetic induction. In magnetostrictive power generation, aleakage magnetic flux due to a change in magnetic field inside amagnetostrictive material in response to applied stress is convertedinto electrical energy through a coil wrapped around themagnetostrictive material. The magnetostrictive power generationinvolves a smaller internal resistance, and generates more power thanthe other types of vibration-based power generation. Anothercharacteristic of the magnetostrictive power generation is the desirabledurability due to the metal alloy used as magnetostrictive material.This makes the magnetostrictive power generation a desirable mode ofpower generation that could overcome an issue associated withmagnetostriction-type vibration powered generators or elements, namely,the durability of magnetostriction-type vibration powered generators orelements.

An example of a magnetostriction-type vibration powered generator is onehaving a cantilever beam structure. A traditional magnetostriction-typevibration powered generator having a cantilever beam structure has amagnetostrictive rod (or a magnetostriction element) formed of amagnetostrictive material; a coil wrapped around the magnetostrictiverod; a magnetic rod disposed parallel to the magnetostrictive rod; aframe curved in a U shape; and a magnet attached to inside of the frame(see WO2015/141414). The frame is a magnetic material with two ends. Oneof the ends on either side of the U-shaped bent portion is a fixed end,and the other end is a free end. In this way, a part of the frame worksas a back yoke, and the frame forms an air gap between the magnet andthe inner surface of the frame where the magnet is not attached.

In such a cantilever beam structure having a fixed end, themagnetostrictive rod is subjected to tensile and compressional stresswhen an external force (vibration) is applied within a horizontal plane,and this creates an alternating magnetic field in the magnetic fieldlines. Voltage is extracted in the form of electrical energy as the coilgenerates voltage in accordance with the law of electromagneticinduction, which states that voltage occurs in proportion to changesoccurring in magnetic flux density over time.

In a magnetostriction-type vibration powered generator, power output Pis represented by P=NI·d/dt(∫iBdA), and power density E is representedby E=P/v. Here, N is the number of turns in the coil, I is the value ofthe current through the coil, B is the magnetic flux density of themagnetostriction element, A is the cross sectional area of themagnetostriction element, and v is the volume of themagnetostriction-type vibration powered generator. However, in themagnetostriction-type vibration powered generator above, the stressexerted on the magnetostriction element in response to an external force(vibration) applied within a horizontal plane in the cantilever beamstructure is greater at the fixed end than at the free end, and thiscreates a stress distribution as a result of the stress not beingexerted throughout the magnetostriction element in a uniform fashion.The stress distribution creates a distribution in the magnetic fieldlines running inside the magnetostriction element, and changes in themagnetic flux density B of the magnetostriction element become smalleras a whole, with the result that the power output P also becomessmaller. That is, the power density E (power output P per volume) is toosmall to achieve the high output (high power output) needed for IoT.Indeed, the power density E of the magnetostriction-type vibrationpowered generator needs to be improved for practical applications. Forexample, a magnetostriction-type vibration powered generator requires aconsumed power density of about 1.0 mW/cm³ in applications such as tireair pressure monitoring systems, and sensor networks for factories.

SUMMARY OF THE INVENTION

The present disclosure is intended to provide a magnetostriction elementand a magnetostriction-type vibration powered generator having a largepower output and a high power density.

According to a first gist of the present disclosure, there is provided amagnetostriction element comprised of a magnetostrictive material thatis a monocrystalline alloy represented by the following formula (1),

Fe _((100-α-β)) Ga_(α)X_(β),   Formula (1)

wherein α and β represent the Ga content (at % ) and the X content (at%), respectively, X is at least one element selected from the groupconsisting of Sm, Eu, Gd, Tb, Dy, Cu, and C, and the formula satisfies5≤α≤40, and 0≤β≤1,

the magnetostriction element having a longitudinal direction along whichthe magnetostriction element extends between opposing first and secondends,

the magnetostriction element having the <100> crystal orientation of themonocrystalline alloy along a direction parallel to the longitudinaldirection, and having a Ga concentration gradient that decreases in adirection from the second end to the first end.

In an aspect of the first gist of the present disclosure, themagnetostriction element may be plate-like in shape.

In an aspect of the first gist of the present disclosure, the Gaconcentration may be 14 at % or more and 16 at % or less at the firstend, and 17 at % or more and 19 at % or less at the second end.

In an aspect of the first gist of the present disclosure, the Gaconcentration may decrease at an average rate of 0.15 at % or more and0.2 at % or less per millimeter in the direction from the second end tothe first end.

In an aspect of the first gist of the present disclosure, X may be atleast one element selected from the group consisting of Sm, Cu, and C,and the formula may satisfy 14≤α≤19, and 0.5≤β≤1.

According to a second gist of the present disclosure, there is provideda magnetostriction-type vibration powered generator comprising a powergenerating section, and a frame joined to the power generating section,

the power generating section having a first end and a second end, andincluding:

-   -   a diaphragm formed of a non-magnetic material and disposed at        the first end of the power generating section;    -   the magnetostriction element of claim 1 disposed at the second        end of the power generating section; and    -   a coil wrapped around the magnetostriction element along the        longitudinal direction,

the frame having a first end and a second end, and including:

a frame body formed of a magnetic material and joined to the second endof the power generating section at the first end of the frame, the framebody extending between the first end and the second end of the frame;and

a magnet provided on the frame body so as to face the magnetostrictionelement of the power generating section,

the magnetostriction element being disposed in such an orientation thatthe direction from the second end to the first end of the powergenerating section corresponds to the longitudinal direction of themagnetostriction element, and that the magnetostriction element joinsthe diaphragm at the first end of the magnetostriction element.

In an aspect of the second gist of the present disclosure, the powergenerating section and the frame may have a C-shape as a whole.

In an aspect of the second gist of the present disclosure, the magnetmay be provided on the frame body so as to face the magnetostrictionelement at the first end of the magnetostriction element.

The present disclosure has provided a magnetostriction element and amagnetostriction-type vibration powered generator having a large poweroutput and a high power density.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a magnetostriction element of anembodiment of the present disclosure.

FIG. 2 is a graph schematically representing a distribution of Gaconcentration in the magnetostriction element of the embodiment of thepresent disclosure.

FIG. 3 is a cross sectional view representing a magnetostriction-typevibration powered generator equipped with the magnetostriction elementof the embodiment of the present disclosure.

FIG. 4 is a perspective view representing the magnetostriction-typevibration powered generator equipped with the magnetostriction elementof the embodiment of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

The following describes a magnetostriction element, and a method ofmanufacture thereof according to an embodiment of the presentdisclosure. A magnetostriction-type vibration powered generator providedwith the magnetostriction element is also described. It is to be notedthat the present disclosure is not limited to the embodiments below.

Magnetostriction Element

The magnetostriction element of the present embodiment is formed of amagnetostrictive material that is a monocrystalline alloy represented bythe following formula (1),

Fe _((100-α-β)) Ga_(α)X_(β),   Formula (1)

wherein α and β represent the Ga content (at %) and the X content (at%), respectively, X is at least one element selected from the groupconsisting of Sm, Eu, Gd, Tb, Dy, Cu, and C, and the formula satisfies5≤α≤40, and 0≤β≤1.

The magnetostriction element has a longitudinal direction along whichthe magnetostriction element extends between opposing first and secondends.

The magnetostriction element has the <100> crystal orientation of themonocrystalline alloy along a direction parallel to the longitudinaldirection, and has a Ga concentration gradient that decreases in adirection from the second end to the first end.

The FeGaX monocrystalline alloy of the formula (1) includes an FeGabinary alloy because β can take a value of 0.

Preferably, X in the formula (1) is at least one element selected fromthe group consisting of Sm, Cu, and C, and the formula satisfies14≤α≤19, and 0.5≤β≤1. In another embodiment, the formula (1) satisfies14≤α≤19, and β=0, preferably 17≤α≤18.4, and β=0.

The magnetostriction element of the present embodiment may have anyappropriately selected shape. For example, the magnetostriction elementof the present embodiment may have a rectangular shape (or a plate-likeshape), a cubic shape, a columnar shape, a polygonal column shape, orsome other solid shape. The preferred shape is a plate-like shape. Inthe case of a plate-like shape, the magnetostriction element may have,for example, cross sectional dimensions measuring 5 mm to 20 mm inwidth, and 1 mm to 3 mm in height, preferably about 10 mm in width, andabout 1 mm in height. The longitudinal length (the distance between theopposing ends along the longitudinal direction) may be 10 mm to 30 mm,preferably about 30 mm, more preferably about 20 mm.

As used herein, “Ga concentration” represents a fraction of the numberof Ga atoms with respect to the total number of atoms in the alloy, andhas a value in at % (atomic percent). More specifically, “Gaconcentration” is a Ga content as measured by analysis of the alloyusing an electron probe microanalyzer (EPMA). Similarly, theconcentrations or contents of the other elements (for example, Fe, Sm,Eu, Gd, Tb, Dy, Cu, and C) in the alloy are measured values in at %(atomic percent) obtained by using the same method. It is to be notedhere that the monocrystalline alloy (an FeGa alloy or an FeGaX alloy)constituting the magnetostriction element of the present embodiment maycontain trace amounts of unavoidable elements (for example, less than0.005 at % of oxygen), provided that the monocrystalline alloy isconfigured essentially from the elements specified above.

As used herein, “gradient” means the presence of an increase or adecrease of a predetermined value, for example, a concentration, along adirection from one specified location to another. Specifically, the term“gradient” as used herein means monotonous decrease or monotonousincrease. To be more specific, in the present disclosure, the Gaconcentration gradient is a measured SPMA value taken end-to-end at thecenter of the magnetostriction element, for example, by a spot analysisat different points of the magnetostriction element, or by a lineanalysis of the magnetostriction element.

In the present disclosure, the <100> crystal orientation of themonocrystalline alloy can be determined by using a known method.However, specifically, the <100> crystal orientation of themonocrystalline alloy is one determined by using an EBSD (ElectronBackscatter Diffraction) technique. The <100> orientation of the FeGaalloy or FeGaX alloy is not easily magnetizable. However, themagnetostriction element is able to produce large magnetostrictionbecause the monocrystalline alloy in the magnetostriction element of thepresent embodiment has the <100> crystal orientation along a directionparallel to the longitudinal direction of the magnetostriction element.The magnetostriction element of the present embodiment can also producelarge magnetostriction when the direction parallel to the longitudinaldirection of the magnetostriction element has a small angle differenceof 10° or less, preferably 6° or less, more preferably 4° or less fromthe <100> crystal orientation of the FeGa alloy or FeGaX alloy. Such amagnetostriction element also represents the magnetostriction element ofthe present embodiment.

The magnetostriction element of the present embodiment is describedbelow in greater detail, with reference to the accompanying drawings.

FIG. 1 is a schematic diagram of a magnetostriction element of anembodiment of the present disclosure. A magnetostriction element 1 isformed of a magnetostrictive material that is a monocrystalline alloyrepresented by the foregoing formula (1). As illustrated in FIG. 1, themagnetostriction element 1 is a plate-shaped element extending along itslongitudinal direction between a first end 1 a at one end of themagnetostriction element and a second end 1 b at the opposite end. Asillustrated in FIG. 1, the magnetostriction element has a spot A at thesecond end 1 b side of the magnetostriction element, a spot B in themiddle, and a spot C at the first end 1 a side of the magnetostrictionelement along the longitudinal direction between the first end 1 a andthe second end 1 b of the magnetostriction element. The magnetostrictionelement 1 has the <100> crystal orientation of the monocrystalline alloyof formula (1) along a direction parallel to the longitudinal direction,and has decreasing Ga concentrations from spot A to spot B and to spot Cwhen measured at these points.

Preferably, the Ga concentration is 14 at % to 16 at % at the first end1 a of the magnetostriction element, and 17 at % to 19 at % at thesecond end 1 b of the magnetostriction element. Preferably, the Gaconcentration becomes smaller from the second end 1 b of themagnetostriction element toward the first end 1 a of themagnetostriction element at an average rate of 0.15 at % to 0.2 at % permillimeter. The Ga concentration at the first end 1 a of themagnetostriction element and at the second end 1 b of themagnetostriction element may be a concentration at a location near theedge (or side) of the magnetostriction element 1. For example, the Gaconcentration is a concentration as measured in a region within 0 to 3mm, typically about 0.5 to 2.5 mm, from the edge of the magnetostrictionelement 1.

FIG. 2 is a graph schematically representing a distribution of Gaconcentration in the magnetostriction element of the embodiment of thepresent disclosure. In FIG. 2, the x axis represents spots A, B, and Cof the magnetostriction element 1, and the y axis represents the Gaconcentration (at %) of the magnetostriction element 1. For example, asschematically represented in the distribution graph, the Gaconcentration of the magnetostriction element 1 of the presentembodiment has a concentration gradient, and monotonously decreases fromspot A to spot C (from the second end 1 b of the magnetostrictionelement to the first end 1 a of the magnetostriction element along thelongitudinal direction).

Because of the Ga concentration gradient, the magnetostriction element 1of the embodiment of the present disclosure shows different magneticcharacteristics (magnetic anisotropy) in the gradient. Specifically, inthe magnetostriction element 1, the extent of magnetic flux densitychange is different at different points of the Ga concentrationgradient. In the present disclosure, a magnetic flux density change dueto applied stress can be measured with a B—H curve measurement deviceinstalled in a tensile-compression tester.

The method used to produce the magnetostriction element 1 according tothe present embodiment is not particularly limited, and anyappropriately selected alloy manufacturing method may be used. Examplesof such methods include the Czochralski technique (CZ technique), theBridgeman technique, and a rapid solidification method. With the CZtechnique, large crystals can be produced with accurate chemicalcompositions and crystal orientations. The Ga concentration gradient inthe magnetostriction element 1 can be created by a skilled personforming the magnetostriction element 1 using, for example, the CZtechnique. For example, the crucible is rotated in the reverseddirection from the direction of rotation of a seed crystal, and eachstep is performed under appropriately adjusted conditions (for example,the rotation speed of the seed crystal and the crucible, and pressure).The concentration can then be measured and confirmed by EPMA analysis.The magnetostriction element 1 can be shaped as desired using any knowntechnique. For example, the magnetostriction element 1 may be cut out bywire discharge machining.

Magnetostriction-Type Vibration Powered Generator

FIG. 3 is a cross sectional view of a magnetostriction-type vibrationpowered generator equipped with the magnetostriction element of theembodiment of the present disclosure. FIG. 4 is a perspective view ofthe magnetostriction-type vibration powered generator equipped with themagnetostriction element of the embodiment of the present disclosure. Asillustrated in FIGS. 3 and 4, a magnetostriction-type vibration poweredgenerator 10 includes a power generating section 2, and a frame 3 joinedto the power generating section 2.

The power generating section 2 has a first end 2 a and a second end 2 b.The frame 3 has a first end 3 a and a second end 3 b. The second end 2 bof the power generating section is joined to the first end 3 a of theframe.

The method used to join the second end 2 b of the power generatingsection to the first end 3 a of the frame is not particularly limited,as long as it does not seriously impair the function of themagnetostriction-type vibration powered generator 10 of the presentembodiment as a whole, specifically, the function that forms anappropriate magnetic circuit. For example, these ends may be fixed toeach other using screws, bolts, nuts, solders, adhesives, or brazingfiller metals, particularly, screws, bolts, or nuts.

The frame 3 has a frame body 3A and a magnet 4. The frame body 3A ismade of a magnetic material, particularly, a ferromagnetic material, andextends between the first end 3 a and the second end 3 b of the frame.For example, the ferromagnetic metallic material may be a cold rolledsteel plate, or a steel band (SPCC, SPCD, SPCE, SPCF, SPCG). The framebody 3A shown in FIGS. 3 and 4 has a C-shape. However, the shape is notparticularly limited, as long as the constituent members are joined toone another, and function as the magnetostriction-type vibration poweredgenerator 10 after manufacture. For example, the power generatingsection 2 and the frame 3, as a whole, may have, for example, a C- or aU-shape after being joined to each other. Specifically, the shape is notlimited, as long as the power generating section 2 extending end-to-endbetween the second end 2 b and the first end 2 a is facing the framebody 3A extending toward the second end 3 b of the frame, and the firstend 2 a (the end on the diaphragm 5 side, specifically, the free end) ofthe power generating section is facing the second end 3 b (the fixedend) of the frame.

The magnet 4 is provided on the frame body 3A, opposite themagnetostriction element1 of the power generating section 2. Preferably,the magnet 4 is provided on the frame body 3A so as to face themagnetostriction element1 at the first end 1 a of the magnetostrictionelement 1. Specifically, the magnet 4 may be provided so as to form anair gap with the magnetostriction element 1. With such an air gap, it ispossible to form a desirable closed magnetic circuit of the magnet 4,the magnetostriction element 1, and the frame body 3A through the airgap. The magnet 4 is not particularly limited, as long as it is asubstance having the property to attract a magnetic material, and thatgenerates a bipolar magnetic field. Examples of such materials include aneodymium magnet, a samarium-cobalt magnet, and an alnico magnet.Preferably, the magnet is a neodymium magnet.

The frame body 3A and the magnet 4 can be installed, for example, simplyby mounting the magnet 4 on the frame body 3A, which is a magneticmaterial. With the magnet 4 mounted on the frame body 3A, the generatedmagnetic force can hold the magnet 4 in place with the magnetic fieldlines running through the frame body 3A. The magnet 4 may be installedor attached using a method involving other types of magnetic forces.When the frame body 3A and the magnet 4 are bonded to each other with anadhesive or other such materials that do not easily pass magnetic fieldlines, the resulting magnetic circuit is reduced in size as suchmaterials become magnetic reluctance.

As illustrated in FIGS. 3 and 4, the power generating section 2 includesa diaphragm 5 and a coil 6, in addition to the magnetostriction element1of the embodiment described above.

The diaphragm 5 is disposed at the first end 2 a of the power generatingsection. The material of the diaphragm 5 is not particularly limited, aslong as it is a non-magnetic material. For example, the diaphragm 5 isconfigured from a non-magnetic material such as a non-magnetic metal(for example, aluminum, titanium, copper, or brass), and a resin (forexample, acrylic resin). By varying the dimensions (length andthickness) of the diaphragm 5 or by attaching a weight to the diaphragm,the spring characteristics of the diaphragm 5 can be altered to adjustthe resonant frequency.

The magnetostriction element 1 is disposed at the second end 2 b of thepower generating section. The magnetostriction element 1, which is themagnetostriction element 1 of the embodiment described above, isdisposed in such an orientation that the direction from the second end 2b to the first end 2 a of the power generating section corresponds tothe longitudinal direction of the magnetostriction element1, and thatthe magnetostriction element joins the diaphragm 5 at the first end 1 a,that is, the end with a lower Ga concentration (in the vicinity of spotC).

In the magnetostriction element 1, the Ga concentration is higher atspot A, and the magnetic flux density difference under no load and underapplied stress is large at spot A when the applied stress is large. Atspot C, where the Ga concentration is lower, the magnetic flux densitydifference under no load and under applied stress is large when theapplied stress is small. Accordingly, the magnetostriction element 1,which is made of an FeGa alloy or an FeGx alloy, can effectively producea large magnetic flux density change as a whole when themagnetostriction element 1 has its second end 1 b, near spot A, disposedon the frame side of the magnetostriction element (fixed-end side) andits first end 1 a, near spot C, disposed on the diaphragm 5 side(free-end side). This is because the configuration of themagnetostriction-type vibration powered generator 10 is such that themagnetostriction element 1 experiences a greater stress at the fixed endthan at the free end. In this way, the magnetostriction-type vibrationpowered generator 10 can have increased power density. In the presentdisclosure, a magnetic flux density difference under no load and underapplied stress means a magnetic flux density difference between themagnetic flux density measured under no load with a B—H curvemeasurement device, and the magnetic flux density measured under appliedtensile or compressional stress with a B—H curve measurement deviceinstalled in a tensile-compression tester.

The method used to attach (or join) the diaphragm 5 to themagnetostriction element 1 is not particularly limited. For example,these may be fixed to each other using, for example, screws, bolts,nuts, solders, adhesives, brazing filler metals, or double-sided tapes.Preferably, the diaphragm 5 and the magnetostriction element 1 are fixedto each other with screws, bolts, nuts, or the like.

The coil 6 is wrapped around the magnetostriction element 1 along thelongitudinal direction of extension of the magnetostriction element1,that is, in a direction from the second end 2 b to the first end 2 a ofthe power generating section. The coil 6 generates a voltage that isproportional to the time-dependent changes occurring in the magneticfield lines running through the magnetostriction element 1, inaccordance with the law of electromagnetic induction. The material ofthe coil 6 is not particularly limited. For example, a copper wire maybe used. A generated voltage can be determined by V=N·dΦ/dt, where N isthe number of turns in the coil 6, and Φ is the magnetic flux.Accordingly, a large voltage can be generated by increasing the amountof magnetic flux change per unit time, or by increasing the number ofturns in the coil 6. The amount of magnetic flux change per unit time isdetermined by the resonant frequency or other mechanical characteristicsof the power-generating element. Accordingly, an easier way ofincreasing the generated voltage of the power-generating element is toincrease the number of turns in the coil 6.

EXAMPLES

The present disclosure is described below in greater detail by way ofExamples and Comparative Examples. The present disclosure, however, isnot limited by the following descriptions.

Example 1

In Example 1, a plate-shaped FeGa-alloy magnetostriction element wasproduced that had varying Ga concentrations along its longitudinaldirection. The magnetostriction element was then measured for magneticflux density under no applied stress and under applied compressionalstress, and changes occurring in magnetic flux density were confirmed.

Production of Magnetostriction Element

In order to produce an FeGa-alloy magnetostriction element of

Example 1-1, iron (purity 99.999%) and gallium (purity 99.999%) wereweighed with an electronic balance. The content of each element in alloyspecimens was measured and adjusted by EPMA analysis.

Specimens were grown using a high-frequency dielectric heating CZfurnace. A dense alumina crucible measuring 45 mm in outer diameter (ϕ)was disposed inside a graphite crucible having an inner diameter ϕ of 50mm, and weighed 400 g of Fe and Ga was supplied as raw materials of eachalloy specimen. The crucibles charged with the raw materials were placedin a growth furnace, and an argon gas was introduced after creating avacuum inside the furnace. Heat was applied as soon as the pressureinside the furnace became atmospheric pressure, and the alloy was heatedfor 12 hours, until a melt was obtained. An FeGa monocrystal was cut toproduce a seed crystal of <100> orientation, and the seed crystal waslowered down to the vicinity of the melt. While being rotated at 5 ppm,the seed crystal was then gradually lowered toward the melt until thetip of the seed crystal contacted the melt. In order to create a Gaconcentration gradient in the specimen, the crucible was rotated at 10rpm in the opposite direction from the seed crystal, and the crystal wasgrown by gradually decreasing temperature, before lifting the seedcrystal at a rate of 1.0 mm/hr. This produced a monocrystalline alloyhaving a Ga concentration gradient and measuring 10 mm in diameter and80 mm in length along the length of its body. For measurement, themonocrystalline alloy was cut into a plate-shaped magnetostrictionelement by wire discharge machining. Here, the plate-shapedmagnetostriction element had cross sectional dimensions measuring 10 mmin width, 1 mm in height, and 20 mm in length (a longitudinal distancebetween the first end and the second end). The longitudinal directionwas parallel to the <100> orientation of the FeGa alloy. This producedthe FeGa-alloy magnetostriction element of Example 1-1 of the shapeshown in FIG. 1 having varying Ga concentrations along the longitudinaldirection.

In order to produce an FeGa-alloy magnetostriction element ofComparative Example 1-1, an FeGa monocrystalline alloy was producedusing the Bridgeman technique, which enables growth of monocrystals of auniform composition. As in Example 1-1, the monocrystalline alloy wascut by wire discharge machining into a plate shape measuring 10 mm×1 mmin cross section and 20 mm in length (a longitudinal distance betweenthe first end and the second end). Here, the longitudinal direction wasparallel to the <100> orientation of the FeGa alloy, as in Example 1-1.

Ga Concentration Measurement of Magnetostriction Elements

The Ga concentrations of the magnetostriction elements of

Example 1-1 and Comparative Example 1-1 were measured by EPMA analysis.Specifically, the Ga concentrations of the FeGa monocrystalline alloyswere measured at spots A, B, and C shown in FIG. 1.

Magnetic Flux Density Measurement of Magnetostriction Element under NoApplied Stress and under Applied Compressional Stress

The magnetostriction elements of Example 1-1 and Comparative Example 1-1were measured for magnetic flux density under no applied stress andunder applied stress (under 5 MPa compressional stress and under 15 MPacompressional stress) at 8 kA/m. Specifically, the magnetic flux densitywas measured for a length of about 2 mm in the vicinity of spots A, B,and C shown in FIG. 1. This was accomplished by using a B—H measurementdevice with a short-length detection coil.

Table 1 shows the results of the Ga concentration (at %; the rest is theFe concentration (at %)) measurements at spots A, B, and C, and theresults of the magnetic flux density (T) measurements for the FeGa-alloymagnetostriction elements of Example 1-1 and Comparative Example 1-1conducted under no applied stress and under applied compressionalstress.

TABLE 1 Ex. 1-1 Com. Ex. 1-1 Ga concentration at spot A [at. %] 18.418.4 Ga concentration at spot B [at. %] 16.9 18.4 Ga concentration atspot C [at. %] 15.4 18.4 Magnetic flux density [T] Near spot A 1.6 1.6under no load Near spot B 1.2 1.6 Near spot C 0.8 1.6 Magnetic fluxdensity [T] Near spot A 1.5 1.5 under 5 MPa compression Near spot B 1.01.5 Near spot C 0.5 1.5 Magnetic flux density [T] Near spot A 0.8 0.6under 15 MPa compression Near spot B 0.7 0.6 Near spot C 0.6 0.6

As shown in Table 1, the Ga concentration was 1.5 at % lower at spot B,and 3 at % lower at spot C than at spot A in Example 1-1. That is,because the magnetostriction element was 20-mm long, themagnetostriction element of Example 1-1 had a composition gradient inwhich the Ga concentration monotonously decreased at 0.15 at %/mm. InComparative Example 1-1, the Ga concentration was 18.4 at % in all ofspot A, B, and C, and the composition was uniform.

In Example 1-1, the magnetic flux density monotonously decreased withthe measured value of 1.6 T at spot A, 1.2 T at spot B, and 0.8 T atspot C under no applied stress. This result is considered to be due tothe decreasing Ga concentrations from spot A to spot C in the FeGa-alloymagnetostriction element of Example 1-1. That is, there appears to be acorrelation between Ga concentration and magnetic flux density. The samecorrelation also should be present under applied compressional stress.Under an applied compressional stress of 5 MPa, the magnetic fluxdensity showed a decrease from 1.5 T at spot A to 1.0 T at spot B, andto 0.5 T at spot C. Similarly, under an applied compressional stress of15 MPa, the magnetic flux density showed a decrease from 0.8 T at spot Ato 0.7 T at spot B, and to 0.6 T at spot C. These results also suggestthat there is a correlation between Ga concentration and magnetic fluxdensity.

In Comparative Example 1-1, the Ga concentration was uniform, with spotsA, B, and C all showing a Ga concentration of 18.4 at %. Here, themagnetic flux density was 1.6 T under no applied stress, and 1.5 T and0.6 T under applied compressional stress (under 5 MPa and under 15 MPa),regardless of the spot, A, B, or C. It can be said from these resultsthat there is a correlation between Ga concentration and magnetic fluxdensity.

The results for Example 1-1 and Comparative Example 1-1 showed thatthere is a correlation between Ga concentration and magnetic fluxdensity in the magnetostriction elements formed of FeGa-alloymagnetostrictive material, and that, with the Ga concentration gradientin the composition of the magnetostriction element, the magnetic fluxdensity also has a gradient, under no applied stress and under appliedcompressional stress. In both Example 1-1 and Comparative Example 1-1,the magnetic flux density was smaller under applied compressional stressthan under no applied stress. This is probably a result of the hinderedmotion of the domain wall inside the magnetostriction element due to theapplied compressional stress to the magnetostriction element formed ofmagnetostrictive material.

Example 2

In Example 2, magnetostriction elements of various Ga concentrationswere produced in the same manner as for the FeGa-alloy magnetostrictionelement of Example 1-1. These were then measured for magnetic fluxdensity under no applied stress and under applied compressional stress,and changes occurring in magnetic flux density were confirmed. For theevaluation of the power density of each magnetostriction element, themagnetostriction element was installed in a magnetostriction-typevibration powered generator of the configuration shown in FIGS. 3 and 4,and measured for power density.

The magnetostriction elements used for measurement had a plate shape asin Example 1-1. The Ga concentrations in the magnetostriction elementshad the values shown in Table 2 at spots A, B, and C as measured by EPMAanalysis (the rest is the Fe concentration (at %)). In Examples 2-1 to2-4, the magnetostriction elements had varying Ga concentrations atspots A, B, and C. The magnetostriction elements of Comparative Examples2-1 and 2-3 had a constant Ga concentration. The magnetostrictionelement of Comparative Example 2-2 had the same Ga concentrations atspots A, B, and C as Example 2-1. The magnetostriction elements wereproduced and cut (wire discharge machining) in the same manner as inExample 1-1. The magnetostriction elements were measured for magneticflux density under no applied stress and applied compressional stress inthe same manner as in Example 1-1.

Evaluation of Power Density in Magnetostriction-Type Vibration PoweredGenerator Equipped with Magnetostriction Element

The magnetostriction elements produced in the manner described abovewere each installed in a magnetostriction-type vibration poweredgenerator of the configuration shown in FIGS. 3 and 4. In Examples 2-1to 2-4 and Comparative Examples 2-1 and 2-3, the magnetostrictionelement was installed in such an orientation that spot C was on thediaphragm side (free-end side), and spot A was on the frame side(fixed-end side). The orientation was reversed in Comparative Example2-2. The magnetostriction-type vibration powered generator equipped withthe magnetostriction element was fitted to a vibrator, and the powerdensity was measured. Specifically, vibration was applied from thevibrator at an acceleration of 2 G. The generated voltage was detectedwith an oscilloscope, and the resonant-frequency power output wascalculated. The power density was then determined by dividing thecalculated value by the size of the magnetostriction-type vibrationpowered generator.

As mentioned above, a magnetostriction-type vibration powered generatorapplied to a tire air pressure monitoring system or a sensor network forfactories requires a consumed power density of at least about 1.0mW/cm³. By using this as a reference, the power density was determinedas being acceptable when the calculated value was 1.0 mW/cm³ or more,and unacceptable when the calculated value was less than 1.0 mW/cm³.

Table 2 shows the measurement results for Examples 2-1 to 2-4 andComparative Examples 2-1 to 2-3, specifically, the Ga concentrations atspots A, B, and C of the FeGa-alloy magnetostriction element, themagnetic flux density under no applied stress and under appliedcompressional stress, the magnetic flux density difference under noapplied stress and under applied compressional stress, the installationdirection of the magnetostriction element in the magnetostriction-typevibration powered generator, and the power density values, along withthe evaluation results.

TABLE 2 Ex. 2-1 Ex. 2-2 Ex. 2-3 Ex. 2-4 Magnetostriction Gaconcentration at spot A [at. %] 19 19 18 17 element Ga concentration atspot B [at. %] 17.5 17 16.5 15.5 Ga concentration at spot C [at. %] 1615 15 14 Magnetic flux density Near spot A 1.65 1.65 1.55 1.2 [T] underno load Near spot B 1.2 1.25 1.15 0.8 Near spot C 0.75 0.85 0.75 0.4Magnetic flux density Near spot A 1.6 1.6 1.4 1.1 [T] under 5 MPa Nearspot B 1.1 1 0.9 0.6 compression Near spot C 0.4 0.45 0.45 0.1 Magneticflux density Near spot A 0.85 0.85 0.8 0.7 [T] under 15 MPa Near spot B0.75 0.7 0.65 0.6 compression Near spot C 0.6 0.55 0.55 0.4 Magneticflux density Near spot A 0.05 0.05 0.15 0.1 difference [T] Near spot B0.1 0.25 0.25 0.2 under no load and Near spot C 0.35 0.4 0.3 0.3 underapplied 5 MPa compression Magnetic flux density Near spot A 0.8 0.8 0.750.5 difference [T] under Near spot B 0.45 0.55 0.5 0.2 no load and underNear spot C 0.15 0.3 0.2 0 applied 15 MPa compression Magnetostriction-Frame side (fixed-end side) Spot A Spot A Spot A Spot A type vibrationDiaphragm side (free-end side) Spot C Spot C Spot C Spot C poweredgenerator Power density [mW/cm³] 2.1 1.9 1.8 1.6 Evaluation resultAcceptable Acceptable Acceptable Acceptable Com. Ex. 2-1 Com. Ex. 2-2Com. Ex. 2-3 Magnetostriction Ga concentration at spot A [at. %] 19 1917 element Ga concentration at spot B [at. %] 19 17.5 17 Gaconcentration at spot C [at. %] 19 16 17 Magnetic flux Near spot A 1.651.65 1.25 density [T] under Near spot B 1.65 1.2 1.25 no load Near spotC 1.65 0.75 1.25 Magnetic flux Near spot A 1.6 1.6 1 density [T] under 5Near spot B 1.6 1.1 1 MPa compression Near spot C 1.6 0.4 1 Magneticflux Near spot A 0.85 0.85 0.7 density [T] under Near spot B 0.85 0.750.7 15 MPa Near spot C 0.85 0.6 0.7 compression Magnetic flux Near spotA 0.05 0.05 0.25 density difference Near spot B 0.05 0.1 0.25 [T] underno load Near spot C 0.05 0.35 0.25 and under applied 5 MPa compressionMagnetic flux Near spot A 0.8 0.8 0.55 density difference Near spot B0.8 0.45 0.55 [T] under no load Near spot C 0.8 0.15 0.55 and underapplied 15 MPa compression Magnetostriction- Frame side (fixed-end side)Spot A Spot C Spot A type vibration Diaphragm side (free-end side) SpotC Spot A Spot C powered generator Power density [mW/cm³] 0.7 0.5 0.4Evaluation result Unacceptable Unacceptable Unacceptable

As shown in Table 2, the power density was 1.0 mW/cm³ or more, and thevalues were acceptable in all of Examples 2-1 to 2-4.

In Example 2-1, the Ga concentration monotonously decreased with themeasured value of 19 at % at spot A, 17.5 at % at spot B, and 16 at % atspot C. The magnetic flux density under no applied stress also decreasedwith the measured value of 1.65 T at spot A, 1.2 T at spot B, and 0.75 Tat spot C. Under applied compressional stress (5 MPa), the magnetic fluxdensity showed a decrease from 1.6 T at spot A to 1.1 T at spot B, andto 0.4 T at spot C. Under applied compressional stress (15 MPa), themagnetic flux density showed a decrease from 0.85 T at spot A to 0.75 Tat spot B, and to 0.6 T at spot C. These results also suggest that thereis a correlation between Ga concentration and magnetic flux density, asin Example 1-1. By focusing on the magnetic flux density differenceunder no applied stress and under applied compressional stress inExample 2-1, the largest magnetic flux density difference under noapplied stress and under an applied compressional stress of 5 MPa was0.35 T, and this occurred at spot C. Under no applied stress and underan applied compressional stress of 15 MPa, the largest magnetic fluxdensity difference was 0.8 T, and this occurred at spot A.

In Example 2-1, the magnetostriction element was installed in themagnetostriction-type vibration powered generator in such an orientationthat spot A, where the magnetic flux density difference under no appliedstress and under an applied compressional stress of 15 MPa (under alarge applied stress) was the greatest and the Ga concentration was thehighest, was on the frame side (fixed-end side), and spot C, where themagnetic flux density difference under no applied stress and under anapplied compressional stress of 5 MPa (under a small applied stress) wasthe greatest and the Ga concentration was the lowest, was on thediaphragm side (free-end side). This is probably the reason for theincreased magnetic flux density change in the FeGa-alloymagnetostriction element as a whole, and the large power density of 1.0mW/cm³ or more.

The same pattern was observed in Examples 2-2 to 2-4. In Example 2-2,the largest magnetic flux density difference under no applied stress andunder an applied compressional stress of 5 MPa was 0.4 T, and thisoccurred at spot C. Under no applied stress and under an appliedcompressional stress of 15 MPa, the largest magnetic flux densitydifference was 0.8 T, and this occurred at spot A. In Example 2-3, thelargest magnetic flux density difference under no applied stress andunder an applied compressional stress of 5 MPa was 0.3 T, and thisoccurred at spot C. Under no applied stress and under an appliedcompressional stress of 15 MPa, the largest magnetic flux densitydifference was 0.75 T, and this occurred at spot A. In Example 2-4, thelargest magnetic flux density difference under no applied stress andunder an applied compressional stress of 5 MPa was 0.3 T, and thisoccurred at spot C. Under no applied stress and under an appliedcompressional stress of 15 MPa, the largest magnetic flux densitydifference was 0.55 T, and this occurred at spot A. As in Example 2-1,the magnetostriction element was installed in the magnetostriction-typevibration powered generator in such an orientation that spot A, wherethe magnetic flux density difference under no applied stress and underan applied compressional stress of 15 MPa (under a large applied stress)was the greatest and the Ga concentration was the highest, was on theframe side (fixed-end side), and spot C, where the magnetic flux densitydifference under no applied stress and under an applied compressionalstress of 5 MPa (under a small applied stress) was the greatest and theGa concentration was the lowest, was on the diaphragm side (free-endside). This is probably the reason for the increased magnetic fluxdensity change in the FeGa-alloy magnetostriction element as a whole,and the large power density of 1.0 mW/cm³ or more.

As shown in Table 2, the power density was less than 1.0 mW/cm³, and thevalues were unacceptable in Comparative Examples 2-1 and 2-3 in whichthe magnetostriction elements of uniform Ga concentration wereinstalled. The smaller power density values are probably due to thesmaller magnetic flux density changes occurring in the magnetostrictionelement as a whole as a result of the stress being distributed over theframe side (fixed-end side) and the diaphragm side (free-end side) ofthe magnetostriction element in the magnetostriction-type vibrationpowered generator, and thus creating a distribution in the magneticfield lines running through the magnetostriction element formed ofmagnetostrictive material. In Comparative Example 2-2, themagnetostriction element was installed in the magnetostriction-typevibration powered generator in such an orientation that spot A, wherethe magnetic flux density difference under no applied stress and underan applied compressional stress of 15 MPa (under a large applied stress)was the greatest and the Ga concentration was the highest, was on thediaphragm side (free-end side), and spot C, where the magnetic fluxdensity difference under no applied stress and under an appliedcompressional stress of 5 MPa (under a small applied stress) was thegreatest and the Ga concentration was the highest, was on the frame side(fixed-end side). This is probably the reason for the decreased magneticflux density change in the FeGa-alloy magnetostriction element as awhole, and the small power density of less than 1.0 mW/cm³. That is, thesmaller power density is considered to be due to the smaller magneticflux density change occurring in the magnetostriction element in themagnetostriction-type vibration powered generator as a whole.

Example 3

In Example 3, the Ga concentration of the FeGa alloy of Example 1-1 wasvaried, and a trace amount of Sm, Cu, or C was added to producemagnetostriction elements. For the evaluation of the power density ofthe magnetostriction element, the magnetostriction element was installedin the magnetostriction-type vibration powered generator in the samemanner as in Example 2, and the power density was measured to confirmthe effectiveness of adding these additional elements.

Evaluation of Power Density in Magnetostriction-Type Vibration PoweredGenerator Equipped with Magnetostriction Element

The magnetostriction elements used for measurement had a plate shape asin Example 1-1. The Ga concentrations (at %) at spots A, B, and C of themagnetostriction elements had the values shown in Tables 3-1 and 3-2(spot A: 19; spot B: 17.5; spot C: 16) and in Tables 4-1 and 4-2 (spotA: 17; spot B: 15.5; spot C: 14) as measured by EPMA analysis. Tables3-1 and 3-2 and Tables 4-1 and 4-2 also show the type of the additionalelement, Sm, Cu, or C, added to the magnetostriction elements ofExamples 3-1 to 3-12, along with the concentrations (at %) of theseelements. The additional element, Sm, Cu, or C, was also added inComparative Examples 3-1 to 3-14. However, in Comparative Examples 3-1,3-2, 3-4 to 3-9, and 3-11 to 3-14, these were added in different amountsfrom the amounts added in Examples. In Comparative Examples 3-3 and3-10, the magnetostriction element was installed in themagnetostriction-type vibration powered generator in the reverseddirection from the other Comparative Examples.

The magnetostriction elements were produced and cut (wire dischargemachining) in the same manner as in Example 1-1. However, the additionalelement, Sm, Cu, or C, was supplied as a raw material to the crucible inthe first step after weighing these elements with Fe and Ga (both have99.99% purity) in the first step. The Sm, Cu, or C content was measuredand adjusted by SPMA analysis, as was the case for Fe and Ga. Themagnetostriction elements had no concentration gradient for Sm, Cu, andC, even though the magnetostriction elements were produced in the samemanner as in Example 1-1. This is probably due to the much lower meltingpoint of gallium compared to the other elements, causing gallium topreferentially vaporize. Another possibility is only the trace amount ofSm, Cu, or C added. The power density of the magnetostriction element inthe magnetostriction-type vibration powered generator was measured andevaluated in the same manner as in Example 2.

Tables 3-1 and 3-2 and Tables 4-1 and 4-2 show the measurement resultsfor Examples 3-1 to 3-6 and Comparative Examples 3-1 to 3-7 and forExamples 3-7 to 3-12 and Comparative Examples 3-8 to 3-14, specifically,the Ga concentrations at spots A, B, and C of the magnetostrictionelement, the type and concentration of the additional element, theinstallation direction of the magnetostriction element in themagnetostriction-type vibration powered generator, and the measuredpower density values, along with the evaluation results.

TABLE 3-1 Ex. 3-1 Ex. 3-2 Ex. 3-3 Ex. 3-4 Ex. 3-5 Ex. 3-6Magnetostriction Ga concentration at 19 19 19 19 19 19 element spot A[at. %] Ga concentration at 17.5 17.5 17.5 17.5 17.5 17.5 spot B [at. %]Ga concentration at 16 16 16 16 16 16 spot C [at. %] Concentration Sm1.0 0 0 0 0.5 0 of additional Cu 0 0.5 0 0 0 1.0 element [at. %] C 0 01.0 0.5 0 0 Vibration Frame side (fixed end) Spot A Spot A Spot A Spot ASpot A Spot A powered Diaphragm side (free Spot C Spot C Spot C Spot CSpot C Spot C generator end) Power density [mW/cm³] 2.3 2.2 2.2 2.2 2.32.4 Evaluation result Acceptable Acceptable Acceptable AcceptableAcceptable Acceptable

TABLE 3-2 Com. Ex. Com. Ex. Com. Ex. Com. Ex. Com. Ex. Com. Ex. Com. Ex.3-1 3-2 3-3 3-4 3-5 3-6 3-7 Magnetostriction Ga concentration at 19 1919 19 19 19231 19 element spot A [at. %] Ga concentration at 17.5 17.517.5 17.5 17.5 17.5 17.5 spot B [at. %] Ga concentration at 16 16 16 1616 16 16 spot C [at. %] Concentration of Sm 1.1 0.4 1.0 0 0 0 0additional Cu 0 0 0 1.1 0.4 0 0 element [at. %] C 0 0 0 0 0 1.1 0.4Vibration Frame side (fixed end) Spot A Spot A Spot C Spot A Spot A SpotA Spot A powered Diaphragm side Spot C Spot C Spot A Spot C Spot C SpotC Spot C generator (free end) Power density [mW/cm³] 0.8 0.9 0.7 0.5 0.70.9 0.8 Evaluation result Unaccept- Unaccept- Unaccept- Unaccept-Unaccept- Unaccept- Unaccept- able able able able able able able

TABLE 4-1 Ex. 3-7 Ex. 3-8 Ex. 3-9 Ex. 3-10 Ex. 3-11 Ex. 3-12Magnetostriction Ga concentration at 17 17 17 17 17 17 element spot A[at. %] Ga concentration at 15.5 15.5 15.5 15.5 15.5 15.5 spot B [at. %]Ga concentration at 14 14 14 14 14 14 spot C [at. %] Concentration Sm1.0 0 0 0 0.5 0 of additional Cu 0 0.5 0 0 0 1.0 element [at. %] C 0 01.0 0.5 0 0 Vibration Frame side (fixed end) Spot A Spot A Spot A Spot ASpot A Spot A powered Diaphragm side (free Spot C Spot C Spot C Spot CSpot C Spot C generator end) Power density [mW/cm³] 1.7 1.8 1.8 1.9 1.71.6 Evaluation result Acceptable Acceptable Acceptable AcceptableAcceptable Acceptable

TABLE 4-2 Com. Ex. Com. Ex. Com. Ex. Com. Ex. Com. Ex. Com. Ex. Com. Ex.3-8 3-9 3-10 3-11 3-12 3-13 3-14 Magnetostriction Ga concentration at 1717 17 17 17 17 17 element spot A [at. %] Ga concentration at 15.5 15.515.5 15.5 15.5 15.5 15.5 spot B [at. %] Ga concentration at 14 14 14 1414 14 14 spot C [at. %] Concentration of Sm 1.1 0.4 1.0 0 0 0 0additional Cu 0 0 0 1.1 0.4 0 0 element [at. %] C 0 0 0 0 0 1.1 0.4Vibration Frame side (fixed end) Spot A Spot A Spot C Spot A Spot A SpotA Spot A powered Diaphragm side Spot C Spot C Spot A Spot C Spot C SpotC Spot C generator (free end) Power density [mW/cm³] 0.5 0.7 0.6 0.4 0.60.5 0.4 Evaluation result Unaccept- Unaccept- Unaccept- Unaccept-Unaccept- Unaccept- Unaccept- able able able able able able able

As shown in Tables 3-1 and 4-1, the power density was 1.0 mW/cm³ ormore, and the values were acceptable in Examples 3-1, 3-2, 3-7, and 3-8in which trace amounts of Sm were added. This is probably due to theincreased magnetic flux density change as a result of improvedsaturation flux density created by (i) the localized strain induced byaddition of Sm having a larger atomic radius than Fe and Ga, and (ii)the magnetic anisotropy produced in the crystals by the quadruple momentof the 4f electron of samarium.

Comparative Examples 3-1 and 3-8, in which samarium was added in anamount of 1.1 at %, had power densities of 0.8 mW/cm³ and 0.5 mW/cm³,respectively, and the values were unacceptable, as shown in Tables 3-2and 4-2. These small power density values are probably due to thesamarium being added beyond the solid solubility limit, and theemergence of the second phase inhibiting the movement of the domain walland reducing the magnetic flux density change.

Comparative Examples 3-2 and 3-9, in which samarium was added in anamount of 0.4 at %, had power densities of 0.9 mW/cm³ and 0.7 mW/cm³,respectively, and the values were unacceptable, as shown in Tables 3-2and 4-2. This is probably because the samarium content was too small tosufficiently improve the saturation flux density.

It can be said from these results that the Sm concentration (at %) mustfall in a range of 0.5 Sm 1.0 to achieve a power density of 1.0 mW/cm³or more.

As shown in Tables 3-2 and 4-2, the power density was 0.7 mW/cm³ inComparative Example 3-3, and 0.6 mW/cm³ in Comparative Example 3-10, andthe values were unacceptable in these comparative examples in whichsamarium was added, and in which the magnetostriction element wasinstalled in such an orientation that spot C of lower Ga concentrationwas on the frame side, and spot A of higher Ga concentration was on thediaphragm side. These small power density values are probably due to thesmaller magnetic flux density change occurring in the magnetostrictionelement as a whole as a result of the reduced magnetic flux densitydifference under no applied stress and under applied compressionalstress due to the installation direction of the magnetostrictionelement, as in Example 2.

As shown in Tables 3-1 and 4-1, the power density was 1.0 mW/cm³ ormore, and the values were acceptable in Examples 3-3, 3-4, 3-9, and 3-10in which trace amounts of copper were added. This is probably a resultof the addition of copper increasing the magnetic anisotropic energy ofthe crystals in the alloy.

As shown in Tables 3-2 and 4-2, the power density was 0.5 mW/cm³ inComparative Example 3-4, and 0.4 mW/cm³ in Comparative Example 3-11, andthe values were unacceptable in these comparative examples in which Cuwas added in an amount of 1.1 at %. These small power density values areprobably due to the copper being added beyond the solid solubilitylimit, and the precipitation of the FeCu-base compound inhibiting themovement of the domain wall and reducing the magnetic flux densitychange.

As shown in Tables 3-2 and 4-2, the power density was 0.7 mW/cm³ inComparative Example 3-5, and 0.6 mW/cm³ in Comparative Example 3-12, andthe values were unacceptable in these comparative examples in which Cuwas added in an amount of 0.4 at %. This is probably because the coppercontent was too small to sufficiently improve the saturation fluxdensity.

It can be said from these results that the Cu concentration (at %) mustfall in a range of 0.5 Cu 1.0 to achieve a power density of 1.0 mW/cm³or more.

As shown in Tables 3-1 and 4-1, the power density was 1.0 mW/cm³ ormore, and the values were acceptable in Examples 3-5, 3-6, 3-11, and3-12 in which trace amounts of carbon were added. This is probably aresult of the addition of carbon inducing tetragonal crystal strain inthe Fe lattice.

As shown in Tables 3-2 and 4-2, the power density was 0.9 mW/cm³ inComparative Example 3-6, and 0.5 mW/cm³ in Comparative Example 3-13, andthe values were unacceptable in these comparative examples in which Cwas added in an amount of 1.1 at %. These small power density values areprobably due to the higher content of carbon than gallium preventingentry of carbon atoms into the Fe lattice and reducing the saturationflux density and the magnetic flux density change.

As shown in Tables 3-2 and 4-2, the power density was 0.8 mW/cm³ inComparative Example 3-7, and 0.4 mW/cm³ in Comparative Example 3-14, andthe values were unacceptable in these comparative examples in which Cwas added in an amount of 0.4 at %. This is probably because the carboncontent was too small to sufficiently induce tetragonal crystal strainin the Fe lattice.

It can be said from these results that the C concentration (at %) mustfall in a range of 0.5≤C≤1.0 to achieve a power density of 1.0 mW/cm³ ormore.

The results of the power density measurement in themagnetostriction-type vibration powered generator equipped with themagnetostriction element prepared by adding one of Sm, Cu, and C to theFeGa alloy confirmed that addition of these additional elements producesa desirable effect, specifically, a power density of 1.0 mW/cm³ or more,when 0.5≤β≤1.0 is satisfied in the formula (1) represented byFe_((100-α-β)) Ga_(α)X_(β), where α and β are the Ga content (at %) andthe X content (at %), respectively.

Because samarium is a rare earth, the same effect should be obtainedwith the rare earths Eu, Gd, Tb, and Dy.

A magnetostriction element of the present disclosure shows largemagnetostriction, and a magnetostriction-type vibration poweredgenerator using the magnetostriction element has high power density.This makes it possible to provide, for example, a magnetostriction-typesensor or a magnetostriction-type actuator that could open the door tomore effective IoT.

What is claimed is:
 1. A magnetostriction-type vibration poweredgenerator comprising a power generating section, and a frame joined tothe power generating section, the power generating section having afirst end and a second end, and including: a diaphragm formed of anon-magnetic material and disposed at the first end of the powergenerating section; a magnetostriction element disposed at the secondend of the power generating section, the magnetostriction elementcomprising a magnetostrictive material that is a monocrystalline alloyrepresented by the following formula (1),Fe_((100-α-β)) Ga_(α)X_(β),   Formula (1) wherein α and β represent Gacontent (at %) and X content (at %), respectively, X is at least oneelement selected from a group consisting of Sm, Eu, Gd, Tb, Dy, Cu, andC, and the formula satisfies 5≤α≤40, and 0≤β≤1, the magnetostrictionelement having a longitudinal direction along which the magnetostrictionelement extends between opposing first and second ends, themagnetostriction element having a <100> crystal orientation of themonocrystalline alloy along a direction parallel to the longitudinaldirection, and having a Ga concentration gradient that decreases in adirection from the second end to the first end disposed at the secondend of the power generating section; and a coil wrapped around themagnetostriction element along the longitudinal direction, the framehaving a first end and a second end, and including: a frame body formedof a magnetic material and joined to the second end of the powergenerating section at the first end of the frame, the frame bodyextending between the first end and the second end of the frame; and amagnet provided on the frame body so as to face the magnetostrictionelement of the power generating section, the magnetostriction elementbeing disposed in such an orientation that the direction from the secondend to the first end of the power generating section corresponds to thelongitudinal direction of the magnetostriction element, and that themagnetostriction element joins the diaphragm at the first end of themagnetostriction element.
 2. The magnetostriction-type vibration poweredgenerator according to claim 1, wherein the power generating section andthe frame have a C-shape as a whole.
 3. The magnetostriction-typevibration powered generator according to claim 1, wherein the magnet isprovided on the frame body so as to face the magnetostriction element atthe first end of the magnetostriction element.